/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jms.core.support;

import javax.jms.ConnectionFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.lang.Nullable;

/**
 * Convenient super class for application classes that need JMS access.
 *
 * <p>Requires a ConnectionFactory or a JmsTemplate instance to be set.
 * It will create its own JmsTemplate if a ConnectionFactory is passed in.
 * A custom JmsTemplate instance can be created for a given ConnectionFactory
 * through overriding the {@link #createJmsTemplate} method.
 *
 * @author Mark Pollack
 * @see #setConnectionFactory
 * @see #setJmsTemplate
 * @see #createJmsTemplate
 * @see org.springframework.jms.core.JmsTemplate
 * @since 1.1.1
 */
public abstract class JmsGatewaySupport implements InitializingBean {

    /**
     * Logger available to subclasses
     */
    protected final Log logger = LogFactory.getLog(getClass());

    @Nullable
    private JmsTemplate jmsTemplate;


    /**
     * Set the JMS connection factory to be used by the gateway.
     * Will automatically create a JmsTemplate for the given ConnectionFactory.
     *
     * @see #createJmsTemplate
     * @see #setConnectionFactory(javax.jms.ConnectionFactory)
     */
    public final void setConnectionFactory(ConnectionFactory connectionFactory) {
        this.jmsTemplate = createJmsTemplate(connectionFactory);
    }

    /**
     * Create a JmsTemplate for the given ConnectionFactory.
     * Only invoked if populating the gateway with a ConnectionFactory reference.
     * <p>Can be overridden in subclasses to provide a JmsTemplate instance with
     * a different configuration.
     *
     * @param connectionFactory the JMS ConnectionFactory to create a JmsTemplate for
     * @return the new JmsTemplate instance
     * @see #setConnectionFactory
     */
    protected JmsTemplate createJmsTemplate(ConnectionFactory connectionFactory) {
        return new JmsTemplate(connectionFactory);
    }

    /**
     * Return the JMS ConnectionFactory used by the gateway.
     */
    @Nullable
    public final ConnectionFactory getConnectionFactory() {
        return (this.jmsTemplate != null ? this.jmsTemplate.getConnectionFactory() : null);
    }

    /**
     * Set the JmsTemplate for the gateway.
     *
     * @see #setConnectionFactory(javax.jms.ConnectionFactory)
     */
    public final void setJmsTemplate(@Nullable JmsTemplate jmsTemplate) {
        this.jmsTemplate = jmsTemplate;
    }

    /**
     * Return the JmsTemplate for the gateway.
     */
    @Nullable
    public final JmsTemplate getJmsTemplate() {
        return this.jmsTemplate;
    }

    @Override
    public final void afterPropertiesSet() throws IllegalArgumentException, BeanInitializationException {
        if (this.jmsTemplate == null) {
            throw new IllegalArgumentException("'connectionFactory' or 'jmsTemplate' is required");
        }
        try {
            initGateway();
        } catch (Exception ex) {
            throw new BeanInitializationException("Initialization of JMS gateway failed: " + ex.getMessage(), ex);
        }
    }

    /**
     * Subclasses can override this for custom initialization behavior.
     * Gets called after population of this instance's bean properties.
     *
     * @throws java.lang.Exception if initialization fails
     */
    protected void initGateway() throws Exception {
    }

}
